Various kinds of data with high information property for a user such as a still image, a moving image. etc. can be displayed as well as character letters such as numerals and characters in a display section of an electronic device of a portable type by the development of a communication technique, a mounting technique, etc. in recent years.
With respect to data displayed in such an electronic device, various kinds of data forms are proposed. For example, in the case of a portable telephone, a technique for receiving or transmitting image data compressed and coded by the standard of a Moving Picture Experts Group (MPEG) is proposed.
In this case, for example, a liquid crystal panel is arranged as a display section of the portable telephone, and a received moving or still image is displayed. Namely, for example, in the liquid crystal panel, the received moving image is displayed in a moving image display area, and the still image such as an explanation with respect to this moving image, operating information, etc. is displayed in a still image display area. There is a liquid crystal driver having a RAM utilized as a frame memory as one example of a display controller for displaying and moving the moving image or the still image with respect to such a liquid crystal panel.
In a memory area of the RAM of the liquid crystal driver, it is necessary to rewrite moving image data in real time to a moving image memory area corresponding to the moving image display area of the liquid crystal panel displaying the moving image. In contrast to this, the still image displayed in the still image display area of the liquid crystal panel is changed by a key operation of the portable telephone, etc. Further, it is necessary to rewrite still image data to be updated to a still image memory area corresponding to the still image display area among the memory area of the RAM of the liquid crystal driver.
Display data (moving image data, or still image data) stored to the RAM of such a liquid crystal driver is read every about 1/60 second in consideration of the visual characteristics of a human being, and the liquid crystal panel is driven. Accordingly, for example, when it is necessary to perform extension processing with respect to compression data as in the MPEG standard and no moving image data can be rewritten to the RAM of the liquid crystal driver corresponding to an area to be displayed at this reading rate of 60 Hz, the same image is continuously read over a plurality of frames.
The inventor in the present invention confirmed a visual recognizing property of the liquid crystal panel being driven by such a liquid crystal driver. It has been found from this visual recognizing property that a level able to visually recognize the moving image to a certain extent lies in a range in which the moving image memory area of the RAM of the liquid crystal driver is rewritten by a frame number exceeding about 20 to 25 frames for one second, i.e., a range in which the same image is continuously read by two frames from the RAM of the liquid crystal driver.
In contrast to this, in the case of a range in which the moving image memory area of the RAM of the liquid crystal driver is rewritten by a frame number equal to or smaller than about 20 to 25 frames for one second, i.e., a range in which the same image is continuously read by at least three frames or more from the RAM of the liquid crystal driver, the moving image displayed and moved by the liquid crystal driver has a feeling of physical disorder in connection with the previous frame, etc. Therefore, a technical problem has been found in the display and movement of the moving image in the liquid crystal panel.